Method of casting ingots



Dec. 4, 1934. N. F. SQRUSSELL ET AL 7 1,982,763

METHOD OF CASTING INGO'IS Filed Jan. 22, 1954 Qg N I Illl A TTORNEXPatented Dec. 4, 1934 UNITED STATES PATENT OFFICE METHOD OF CASTINGINGOTS Application January'22, 1934, Serial No. 707,750

2 Claims. (Cl. 22-192) Our invention relates to the casting of metalingots in metallic molds and particularly, though not excl 1 .vely, tothe casting of steel ingots. The molds used for the casting of ingotsare 5 generally of cast iron and to prevent adherence between the moldand the ingot and, in the case of steel ingots, liability to impair theportion of the mold in contact with the steel poured into the mold, itis the usual practice to coat the inside of the mold with anonconducting coating by spraying or otherwise applying a liquid mediumcharged with finely divided mold coating material against the walls ofthe mold until a coating of suflicient thickness is deposited upon themold wall after which and before the molten metal is poured into themold and the liquid medium is partly driven off and partly solidified tobring about the formation of a dry incrustation over the mold surface.In applying the coating in this way, considerable time is requiredbecause the mold after being used for the casting of an ingot is veryhighly heated and must be'permittedto cool down to a considerable extentbefore the coating is applied and because, again, the coating must bepermitted to dry and harden before metal is again poured into the ingotmold. Again, in coating molds in this manner, it .is impracticable toobtain a really smooth surface in the coating and this 30 leads to anundesirable roughness in the surface of the ingot and there is also anundesirable liability for portions of the crusted coating to becomeimbedded in and adherent to the ingot while portions of the crustedcoating are also 35 liable to become quite firmly attached to the moldsurface which leads to further inequalities in successive coatingsapplied to the mold. Again, the adherence of portions of the coating tothe ingot and of portions of the coating to 40 the mold opposesresistance to the withdrawal of the ingot from the mold.

The object of our invention is to cut down the interval betweensuccessive uses of a mold for the casting of an ingot.under conditionswhich will provide for the ingot having a smooth metallic'surface with aminimum of adherent mold coating material and to facilitate the readywithdrawal of a cast ingot from its mold and we have discovered that allof these purposes can be effected by depositing upon the walls of themold a coating of loosely adherent and loosely coherent dry particles ofmold coating material byprogresslvely directing against successivecontiguous portions of the mold surface a jet of a carrier gas chargedwith finely divided dry particles of mold coating material and thenafter the surface of the mold has been thus coated, pouring the liquidmetal into the coated mold in progressive contact with the coatedsurface until the mold has been charged to the desired extent .60 andthen, after the ingot has solidified, withdrawing it from the coatedmold.

The thickness of the coating which it is desirable to apply to the moldsurface by the method which we have described will vary somewhat withthe size of the ingot but by building up the coating from the bottom ofthe mold upward by progressively directing the carrier gas jet firstagainst the bottom portions of the walls of the mold and thenprogressively upward against the successively contiguous surfaces of themold the coating so applied is, to 'a certain extent, self supportingpartly in view of the fact that the walls of an ingot mold flare upwardto facilitate the withdrawal of the ingot from the mold and we havefound that by coating the mold in this way it is entirely practicable tobuild up a coating of ample thickness to serve the purposes for which acoating is applied. 86

In coating molds in the manner which we havi! described a certain amountof the coating material with which the carrier gas jet is charged willnot be so impacted against the walls of the mold as to form an adherentportion of the coating but will fall to the bottom of the mold and forma coating over the bottom and the formation of this bottom coating wehave found to be not detrimental but, on the contrary, advantageous asit is covered by that portion of 90 the metal, which is first pouredinto the mold and entrapped between the molten metal and the bottom ofthe mold.

It is practicable to use in our method a wide varietyof mold coatingmaterials. Thus, we have successfully used finely divided ferro-silicon,silica flour, calcium silicide, kaolin, ferro manganese and magnetiteand we have found ferro-silicon and silica flour especially well adaptedfor our purpose. It will be understood that the materials used to form acoating should be such as are not materially affected by the wtemperatures to which they are subjected either during application tothe mold surface or by reason of their contact with the molten metal sothat they retain their fine state of division and loose cohesion afterthe casting of the ingot and thus facilitate the withdrawal of the ingotfrom the mold and so also that the adhesion of the coating material tothe cast ingot will not take place to any detrimental extent.

In our patent, granted March 6, 1934, Number. 1,949,433, we havedescribed and claimed as our coating material and then pouring themolten metal to form the casting into the so coated mold, preferably andfor the best results as promptly after the deposition of the coatingmaterial upon the mold surface as is practicable. We have also, in oursaid former patent, pointed out that in the case of cast iron pipes thebest results are obtained when the depth of the deposited coating is notsubstantially greater than that which isfound to be sufllcient toprevent the formation of a chill on the outer surface of the cast pipeand we have also pointed out that the liability of the coating to flakeoff from the surface of the mold or to be fractured by the impact of themetal poured into the mold increases with the thickness of the coatingdeposited upon the mold and we have noted the observed fact thatadsorbed films of the carrier gas by means of which the coating materialis deposited upon the mold surface form in the newly deposited coating anot unimportant constituent of the coating. In our method of castingingots and particularly steel ingots, it is practicable and desirable tocoat the molds to a considerably greater depth than is either desirableor even practicable in the case of centrifugal metal molds used in thecasting of cast iron pipes and the only precautions which need be had inview are that the thickness of the coating should be sufiicient toprevent such a rapid transfer of heat from the molten metal to the moldas would result in fusion taking place on the surface of the mold andthat the thickness of the coating should not exceed that at which, owingto the loose cohesion of the particles, flaking off of the depositedcoating and consequent contact between the molten metal and the moldsurface would be liable to occur. The efflcient and cohesivestability'of the coating will vary to some extent with the character ofthe coating materials used but is readily ascertained and, as agenerally applicable rule, we would state that good results can beobtained by progressively delivering during the coating of the moldsurface an amount of coating material which, if compactly distributedover the coated surface, will form a coating of approximately fifteenthousandths of an inch in thickness.

While it is practicable and will generally be advantageous to pour themolten metal into the coated mold promptly after the mold is coated, itis by no means so important in the case of the casting of ingots as itis in the case of casting centrifugally cast cast iron pipes because thepresence of occluded films of gas in the coating is not, we believe, soimportant in the casting of ingots as in the casting of such pipes and,while not without influence, may perhaps be disregarded owing to thefact that the coating applied to the ingot comprises a much greaterquantity of solid coating material than is either desirable orapplicable in the centrifugal casting of pipes.

We have in our said former patent noted the fact that the jet of chargedcarrier gas directed against the mold surface to be coated should be soregulated in volume and velocity that while it imparts su'flicientvelocity to the solid particles with which it is charged to bring theminto contact with the mold surface the gas jet itself shall not impactagainst the mold surface with suflicient energy to blow away the looselyadherent and coherent particles of finely divided dry coating materialdeposited upon the mold surface and this, of course, is true with regardto the coating of ingot molds and having in view this essentialprecaution a carrier gas jet of any form progressively directed againstsuccessive contiguous portions of the ingot mold to be coated may beused and the jet nozzle from which the jet of carrier gas is projectedmay be given the necessary relative movement with respect to the surfaceof the mold to be coated to bring the jet into progressive contact withsuccessive contiguous portions of the mold in any convenient way.

As an aid to the understanding of our process and an example of simpleand effective apparatus for its practice, we would refer to the drawingforming a part of this specification in which Figure 1 is a diagrammaticelevation of apparatus adapted for the practice of our process shownpartly in section.

Figure-2 is a cross-section on the line 2-2 of Fig. 1.

Figure 3 is a fragmentary sectional elevation of a detail of theconstruction shown in Fig. 1, and

Figure 4 is a cross-section on the line 4-4 of Fig. 3.

A is a section of a track loop on which, as shown, are supported threecars indicated at A A and A each supporting an ingot mold, indicated atB, B and B The walls of the mold indicated at B preferably flare fromthe bottom upward to facilitate'the withdrawal of the ingot. At C wehave indicated an adherent coating of finely divided dry coatingmaterial deposited upon the sides of the mold and at C we have indicatedthe coating material as deposited upon the bottom of the mold. Inregistry with the car A we have indicated an overhead structureconsisting of a platform D supported as by beams, one indicated at D,the platform D having a passage D formed through it, through whichextends an externally threaded 130 tube E having a longitudinal key-wayE formed through its threads. The threadsof this tube are engaged withthe internal threads F of a block F, supported, as shown, on theunder-side of the platform D. G is a gear wheel fitting around thethreaded tube E and having a key G fitting in the key-way E of the tube.This gear wheel is supported, as shown, in a forked bracket G secured,as shown, to the upper portion of the platform D. The gear wheel G isrotated by means of a pinion G driven by a motor indicated at Gsupported on the platform D. H is a conduit pipe for a carrier gaspassing through the center of the tube E and secured to movelongitudinally and rotatable with the threaded tube as by means ofspiders indicated at H H To the lower end of the pipe H is secured anozzle H adapted to deliver a carrier gas jet horizontally and, asshown, the nozzle is secured to the end of the pipe H by an 150 ofisetconnection H the purpose of which is to bring the nozzle into closerproximity with the walls of the mold. At the upper end of the pipe H, Ihave diagrammatically indicated a swivel joint at J, by means of whichthe pipe is connected to a hose J which, in turn,"is connected to a gunJ, to which a jet of gas underpressure is. delivered by a nozzle Jhaving, as shown, a cock J and pressure gauge J J indicates themechanism for feeding finely divided dry coating material to a hopperindicated at J", through which it is delivered to the inside of the gun.The gun and its connections are projecting lug on the top of thecompleted ingot, as shown at M on the ingot M formed in the mold B. Atthe left hand side of Fig. 1 we have shown the lug M as engaged bylifting tongs indicated at N and by means of which the ingot can bedrawn up out of the mold.

In operation, the ,car A for example, supporting a mold B is broughtinto registry with the threaded tube E which, of course, is retracted topermit the mold to pass beneath it; then, by preference, the gear wheelG is rotated by its connected motor to rotate the threaded tube E sothat it will screw down inthe internally threaded block F until thenozzle H is projected into the mold to a point near the bottom of themold. Gas under pressure from a source not shown is then poured throughthe,

nozzle J as by opening the valve J and the feeding device for finelydivided dry coating material is set in operation to feed the coatingmaterial to the gun J, with the result that a Jet of carrier gas chargedwith finely divided dry coating material is delivered through the hose Jto the pipe H and issues as a Jet through the nozzle H", the jet beingdirected against the side of the ingot mold. The gear wheel G is thenrotated in an opposite direction to that in which it feeds the threadedtube downward with the until the mold is thoroughly coated frombotto'mto top and the bottom will have a layer, indicated at 0 formedupon it by the particles of coating material which do not adhere to thesides of the mold. When the mold has been coated as described, itssupporting car is moved into registry with the pouring ladle,asindicated at A, a hot top L placed upon the top of the mold and moltenmetal permitted to flow from the ladle into the mold by opening thevalve K By preference, the metal is poured until the mold is fullychargedand the lock M formed upon its tube. When the ingot has hardened,the hot top is removed and the car shifted to a position indicated at Ain which the ingot is removed from the mold, which may be done in anyconvenient way, as indicated by means of tongs N.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent, is:

1. In the casting of metal ingots in metallic ',molds the method stepswhich consist in building up upon the walls of the mold a looselyadherent and loosely coherentcoating of finely divided dry mold coatingmaterial by progressively directing against successive contiguous areasof the upright surface of the mold a jet of a carrier gas charged withfinely divided dry particles of mold coating material, then pouringmolten metal into the so coated mold and after the ingot has solidifiedwithdrawing the ingot 5 from the mold.

2. The method of claim 1, in which the charged jet of carrier gas isinitially directed against the bottom portion of the upright walls ofthe mold and progressively moved upward in 0 the mold so as toprogressively coat the mold from the bottom upward.

NORMAN 'F. s. nussmf" mnnmrox c. momma.

